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In many communication systems, RF signals need to travel tens of kilometers. At lower frequencies coaxial cables are still usable, but once you move into the multi-GHz range, loss and interference quickly become unacceptable.

RFoF (Radio over Fiber) addresses this by directly modulating RF signals onto an optical carrier, sending them through fiber, and recovering them at the remote end. This combines the low loss and wide bandwidth of optical fiber with the simplicity of bypassing additional frequency conversions.

Frequency Range and Link Characteristics

A typical 6 GHz RFoF module covers 5 MHz – 6000 MHz. End-to-end link gain is about 22 dB, with flatness within ±2.5 dB across the full band. Over a narrower 36 MHz span, flatness can be as good as ±0.25 dB. This matters for multi-carrier or broadband signals, since flatter response reduces equalization overhead.

Dynamic Range and Noise

Two key metrics for any RFoF link are the noise figure (NF) and the spurious-free dynamic range (SFDR).

• NF is around 16 dB, which allows weak signals to remain usable after transport.
• SFDR is about 104 dB·Hz^(2/3), indicating how well the link can handle strong and weak signals together without distortion.

For example, in a 10 MHz bandwidth, this translates to an effective dynamic range on the order of 70–80 dB—sufficient for most fronthaul and satellite reception scenarios.

Environmental and Interface Considerations

These modules typically operate from –20 °C to +75 °C, with storage limits from –40 °C to +85 °C. Common interfaces include FC/APC optical connectors, with selectable wavelengths at 1310 nm or 1550 nm. Power is usually 5 V at ~150 mA, keeping power consumption low and integration straightforward.

Application Scenarios

• 5G / LTE fronthaul: linking base stations and remote RF units with low latency and high bandwidth;
• Satellite ground stations: carrying high-frequency signals from antenna sites to control rooms;
• CATV / HFC networks: replacing coax over long spans to reduce attenuation;
• Research facilities: radio telescopes and other low-noise signal transport needs.

Conclusion

RFoF is not a universal solution, but when frequencies extend into the GHz range and distances span kilometers, it offers clear advantages: wide bandwidth, low loss, and strong dynamic range. Understanding link budget and parameter trade-offs is key to building reliable systems.

Full specifications can be found in the technical datasheet.